Methods & Experiments

Generation and Shaping of mid-infrared light pulses

Intense few-cycle pulses at mid-infrared (MIR) wavelengths provide a powerful tool for the phase control of condensed matter. One important parameter for the description of the electric field of such few-cycle pulses is the carrier envelope phase (CEP), which defines the temporal offset of the peak of the intensity envelope from the nearest peak of the carrier wave. The generation of pulses with reproducible electric field, necessary for some of our experiments, calls for the control of the CEP.

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Generation of high-intensity Terahertz pulses

Coherent control of complex materials with intense THz pulses is particularly challenging, due to the lack of pulsed THz sources with sufficient field strength. The THz pulse energies generated by optical rectification sources or photoconductive switches pumped by amplified laser pulses are typically on the order of hundreds of picojoules, with field strengths of ~1 kV/cm. In our strong field THz experiments we use two different generation mechanisms which provide µJ pulse energies electric fields of hundreds of kV/cm, thus allowing to study nonlinear phenomena:

- Tilted pulse front excitation in LiNbO3 crystals
- Narrow-bandwidth multi-cycle pulses from Free-Electron-Lasers
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Femtosecond X-ray Diffraction Techniques

We make use of time-resolved diffraction techniques to investigate both, the structural dynamics of the crystal lattice, and the dynamics of electronic, orbital and spin ordering in complex oxides following their optical excitation.

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Time and angle resolved photoemission spectroscopy

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing electronic structure as a function of momentum and energy in solids.

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Broadband Time-resolved terahertz spectroscopy

In our laboratories we perform systematically time-resolved experiments using broadband THz probe pulses generated with different techniques:

- Optical rectification in non-linear crystals
- Photoconductive switches
- Gas plasma

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Ultrafast optics under high pressure

The application of external pressure on a solid can be used to continuously tune structural or electronic parameters. In particular in superconductors pressure can drive the compounds towards or away from lattice instabilities by varying relevant parameters for the superconducting properties and thus tuning the critical transition temperature Tc.

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